PT-2025-21347 · Vyper · Vyper

Th3Anatomist · Published 2025-05-15 · Updated 2025-05-16 · CVE-2025-47285

Positive Technologies (AI Summary)

CVSS v4.0

6.3

Medium

Base vector

AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N

Name of the Vulnerable Software and Affected Versions: Vyper versions up to and including 0.4.2rc1

Description: The issue arises from the concat() function potentially skipping the evaluation of side effects when the length of an argument is zero. This is due to a fastpath in the implementation that skips the evaluation of argument expressions when their length is zero. Typically, zero-length bytestrings are constructed with the empty literal b"", and it would be unusual for user code to construct zero-length bytestrings using expressions with side effects. However, such side effects could be introduced using the ternary operator, for example, b"" if self.do some side effect() else b"".

Recommendations: For versions up to and including 0.4.2rc1, as a temporary workaround, avoid having side effects in expressions that construct zero-length bytestrings. Update to version 0.4.2 or later, which is expected to include the fix available in pull request 4644.

Exploit

Fix

Weakness Enumeration

CWE-691

Related Identifiers

CVE-2025-47285

GHSA-QHR6-MGQR-MCHM

Affected Products

Vyper

References · 9

• 🔥 https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/47xxx/CVE-2025-47285.json · Exploit
• https://nvd.nist.gov/vuln/detail/CVE-2025-47285 · Security Note
• https://osv.dev/vulnerability/GHSA-qhr6-mgqr-mchm · Vendor Advisory
• https://osv.dev/vulnerability/CVE-2025-47285 · Vendor Advisory
• https://github.com/vyperlang/vyper/blob/68b68c4b30c5ef2f312b4674676170b8a6eaa316/vyper/builtins/functions.py#L560-L562 · Note
• https://github.com/vyperlang/vyper/security/advisories/GHSA-qhr6-mgqr-mchm · Note
• https://github.com/vyperlang/vyper/pull/4644 · Note
• https://github.com/vyperlang/vyper · Note
• https://twitter.com/CVEnew/status/1923073525646028983 · Twitter Post